Why are the low birtweight rates in Brazil higher in richer than in poorer municipalities??: Exploring the epidemiological paradox of low birthweight - Silva, Antônio A. M.; Bettiol, Heloisa; Barbieri, Marco Antonio; Pereira, Márcio M.; Brito, Luiz Gustavo Oliveira; Ribeiro, Valdinar S.; Aragão, Vânia M. F. (Paediatric and Perinatal Epidemiology, 2005)